Average Follow-up Time DetailParticipants were followed-up for a mean of 3.5 years (SD=1.54).

Exposure DetailTotal daily exercise and nonexercise physical activity was measured 24 hours/day for up to 10 days with actigraphs worn on the nondominant wrist. Physical activity was measured with actigraphy(Actical®; Mini Mitter, Bend, OR). Total daily physical activity was the average sum of all daily activity counts recorded[13]. On average, there were more than 3 x 10^5 activity counts/day; raw counts were divided by 1 x 10^5 (about 1 SD) to facilitate presentation and interpretation of the results.

"Cognitive function was assessed using a battery of 19 tests which were used to create a composite measure of global cognition as described elsewhere[12]. Cognitive testing was scored by computer and reviewed by a neuropsychologist to diagnose cognitive impairment. Participants were then evaluated by a clinician who used all cognitive and clinical data to diagnose AD using National Institute of Neurological and Communicative Disorders and Stroke–Alzheimer’s Disease and Related Disorders Association criteria."

"Next, we examined the association of total daily physical activity with incident AD using a discrete-time Cox proportional hazards model with terms that adjusted for age, sex, and education[18]. Next we added terms to this core model to examine potential confounders and modifiers."